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Fencer Intel
high 8.1

CVE-2026-88011 json

Traefik: ForwardAuth identity spoofing via dot-form header alias

published 2mo ago modified last mo. also CVE-2026-88879 , GHSA-rf44-j88r-hh8c , GO-2026-6455 , EUVD-2026-75584

cvss
8.1
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 36%
public exploits
0
none known

Summary

Traefik is an open source HTTP reverse proxy and load balancer. Prior to 2.11.56, and from 3.0.0 until 3.7.12, a client-supplied dot-form header such as X.Authenticated.User survives ForwardAuth replacement and underscoreHeadersStrategy because Go treats it as distinct from X-Authenticated-User while normalization-prone CGI, WSGI, PHP, and NGINX backends collapse both names. A backend can consequently consume the client value instead of the identity Traefik asserted, allowing identity spoofing for any header managed by Traefik. The aliasHeadersStrategy protection is disabled by default and must be configured as delete or reject. The mitigation is available in 2.11.56 and 3.7.12.

Patch / fix

  • go github.com/traefik/traefik/v2 2.11.56
  • go github.com/traefik/traefik/v3 3.7.12
  • traefik traefik 2.11.56, 3.7.12
  • govulncheck-vulndb SLES 16.0, SLES for SAP applications 16.0 0.0.20260916T180043-160000.1.1

suse advisories SUSE-SU-2026:23855-1SUSE-SU-2026:23863-1

  • govulncheck-vulndb openSUSE Leap 16.0 0.0.20260916T180043-160000.1.1

opensuse advisories openSUSE-SU-2026:21897-1

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-88011 updated cvss 9.1

github.com/traefik/traefik: Traefik: Identity spoofing via dot-form header alias

  • Red Hat OpenShift Dev Spaces 3.31 devspaces/traefik-rhel9 1792464177
    fixed: vendor fix RHSA-2026:90321
  • Red Hat OpenShift Dev Spaces 3.31 devspaces/udi-rhel9 1792708612, devspaces/code-rhel9 1792599388, devspaces/server-rhel9 1792775639, devspaces/openvsx-rhel9 1792494821, devspaces/udi-base-rhel9 1792686842, devspaces/code-sshd-rhel9 1792598059, +9 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
last mo.

Exploit prediction

0.42% chance of exploitation in the next 30 days, higher than 36% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
CNA 4.0 5.3 CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N
CNA 4.0 5.3 CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
NVD 3.1 8.1 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

Affected packages

ecosystem package affected fixed in
go github.com/traefik/traefik/v2
<2.11.56
2.11.56
go github.com/traefik/traefik/v3
>=3.0.0, <3.7.12
3.7.12
go github.com/traefik/traefik
all versions
 no fix listed

Affected products

  • traefik traefik

Classification

Weakness
  • CWE-290 Authentication Bypass by Spoofing

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.